This Background is intended to provide the basic context of this patent application and it is not intended to describe a specific problem to be solved.
Two participants, such as a personal computer and a display device may be able to communicate over a channel that offers no physical proximity information (i.e., IP networking). There is no way to guarantee that the other party is physically proximal to the first party. The devices could be in the same room or across the world. In some cases, physical proximity is sufficient to guarantee a minimum (but not comprehensive) trust boundary. For example, it would be useful to limit access to an IP connected projector to a PC within range of a specific wifi beacon in the building.